4T65E and 4T65E HD (99+) N-Body Swap

So you have significantly modded your engine and now your transmission seems to be the weak link of your build. You have a few options to upgrade the stock 4T45E transmission which can be rather costly, or you can swap to the stronger 4T65E series transmission which seems to be uncharted territory for many. The purpose of this article is to provide a little more insight on what it will take to swap a 4T65E transmission into your 99+ N-body.

Major Items Required:

• · 4T65E or 4T65E HD Transmission
• · Mounts (purchased or custom fabricated)
• · Torque Convertor (99-05 Grand Am GT)
• · Transmission dipstick Tube & Indicator (95+ Grand Prix)
• · Inspection Cover (95+ Grand Prix)
• · Gear Selector Lever (95+ Grand Prix)
• · Nose Cone Bracket (95+ Grand Prix)
• · Trans Cooler Lines (95+ Grand Prix)
• · Axles Pieces Sourced from Various Vehicles
• · Tuning Package (to reprogram PCM)

Important Considerations When Picking your Transmission:

• When picking your transmission you should look for a 98-02 transmission (See Appendix I).
• The 4T65E transmission is more common and can be found with 3.29 drive ratio, which is preferred for this swap as it matches the stock gear ratio on the 99+ Grand Am GT model. This will be most likely the most affordable route and if desired the HD differential can be added.
• The 4T65E HD transmissions can be somewhat harder to find and were only available with a 2.97 drive ratio. On the concept cars, GM engineers swapped out the internal input/ output gears 37/33 tooth for 35/35 tooth units. This change will raise the 4T65 HD 2.97 ratio to 3.29.